U.S. patent number 8,295,303 [Application Number 10/109,643] was granted by the patent office on 2012-10-23 for system and method for transmission of frame relay communications over a digital subscriber line equipped with asynchronous transfer mode components.
This patent grant is currently assigned to Verizon Business Global LLC. Invention is credited to Robert L. Demaria, Colleen M. Green, Donald B. Roberts.
United States Patent |
8,295,303 |
Demaria , et al. |
October 23, 2012 |
System and method for transmission of frame relay communications
over a digital subscriber line equipped with asynchronous transfer
mode components
Abstract
A system and method for transmitting Frame Relay based
communication over an ATM based network that includes a DSL link
are disclosed. The Frame Relay based communication is mapped into
ATM cells at a Digital Subscriber Line Access Multiplexer (DSLAM).
The mapping of the Frame Relay frames into ATM cells is carried in
accordance with transparent mode or translation mode functionality
provided in the DSLAM. The Frame Relay data may be mapped into the
ATM cells pursuant to FRF.5, FRF.8, FRF.8.1, or other similar
standards. The system and method may enable transparent propagation
of the Frame Relay data across the DSL/ATM network, for receipt on
the other end of the network by a Frame Relay compatible switch, or
an ATM compatible switch.
Inventors: |
Demaria; Robert L. (Elizabeth,
CO), Green; Colleen M. (Aurora, CO), Roberts; Donald
B. (Aurora, CO) |
Assignee: |
Verizon Business Global LLC
(Basking Ridge, NJ)
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Family
ID: |
26807195 |
Appl.
No.: |
10/109,643 |
Filed: |
April 1, 2002 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20020159462 A1 |
Oct 31, 2002 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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60279669 |
Mar 30, 2001 |
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Current U.S.
Class: |
370/466; 370/401;
370/352 |
Current CPC
Class: |
H04L
12/4633 (20130101); H04L 12/2883 (20130101); H04L
12/2856 (20130101); H04L 12/5601 (20130101); H04L
2012/567 (20130101); H04L 2012/5618 (20130101); H04L
2012/5606 (20130101) |
Current International
Class: |
H04J
3/22 (20060101); H04L 12/28 (20060101); H04L
12/66 (20060101) |
Field of
Search: |
;370/401,466 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Lane, J., "Personal Broadband Services: DSL and ATM", Virata, 1998.
cited by other .
"Frame Relay/ATM PVC Service Interworking Implementation Agreement
FRF.8.1", Frame Relay Forum Technical Committee, Feb. 28, 2000.
cited by other .
"Frame Relay/ATM PVC Service Interworking Implementation Agreement
FRF.5", Frame Relay Forum Technical Committee, Dec. 20,1994. cited
by other .
"Frame Relay/ATM PVC Service Interworking Implementation Agreement
FRF.8", Frame Relay Forum Technical Committee, Apr. 14, 1995. cited
by other.
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Primary Examiner: Wong; Warner
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application is related to and draws priority on prior
U.S. provisional patent application Ser. No. 60/279,669, filed Mar.
30, 2001, and entitled: System and Method for Frame Relay and
Asynchronous Transfer Mode Date Transmission Over a Digital
Subscriber Line, which application is incorporated herein in its
entirety by reference.
Claims
What is claimed is:
1. A system for transmitting a Frame Relay based communication over
an Asynchronous Transfer Mode (ATM) based network that includes a
Digital Subscriber Line (DSL) link, comprising: a Digital
Subscriber Line Access Multiplexer (DSLAM) operatively connected to
a Customer Premises Equipment (CPE) device, the DSLAM operatively
connecting to an ATM network; and a Frame Relay capable switch
connected to the ATM network, wherein the DSLAM is adapted to map
Frame Relay based communication frames into ATM cells for
transmission over the ATM network.
2. The system of claim 1, wherein the Frame Relay capable switch is
adapted to convert the Frame Relay based communication mapped into
ATM cells back into Frame Relay based communication frames.
3. The system of claim 1 wherein the CPE device comprises an xDSL
router.
4. The system of claim 1 wherein the CPE device comprises an xDSL
compatible Data Service Unit (DSU).
5. The system of claim 1 wherein the DSLAM is adapted to map Frame
Relay based communication frames into ATM cells in accordance with
an FRF.5 standard.
6. The system of claim 1 wherein the DSLAM is adapted to map Frame
Relay based communication frames into ATM cells in accordance with
an FRF.8 standard.
7. A method comprising: receiving a Frame Relay based communication
from a Digital Subscriber Line (DSL) compatible Customer Premises
Equipment (CPE) device at a Digital Subscriber Line Access
Multiplexer (DSLAM); mapping the Frame Relay based communication
into Asynchronous Transfer Mode (ATM) cells at the DSLAM; and
transmitting, via the DSLAM, the ATM cells across an ATM network to
a Frame Relay capable switch.
8. A method comprising: receiving a Frame Relay based communication
from a Digital Subscriber Line (DSL) compatible Customer Premises
Equipment (CPE) device at a Digital Subscriber Line Access
Multiplexer (DSLAM); mapping the Frame Relay based communication
into Asynchronous Transfer Mode (ATM) cells at the DSLAM;
transmitting, via the DSLAM, the ATM cells across an ATM network to
an ATM capable switch.
9. The method of claim 7 further comprising: recovering the Frame
Relay based communication from the ATM cells at the Frame Relay
capable switch.
10. The method of claim 7 wherein the mapping includes: mapping the
Frame Relay based communication frames into ATM cells in accordance
with an FRF.5 standard.
11. The method of claim 7 wherein the mapping includes: mapping the
Frame Relay based communication frames into ATM cells in accordance
with an FRF.8 standard.
12. The method of claim 7 wherein the mapping includes: mapping the
Frame Relay based communication frames into ATM cells in accordance
with an FRF.8.1 standard.
13. The method of claim 7 wherein the mapping is transparent to the
DSL compatible CPE device.
14. The method of claim 8 further comprising: recovering the Frame
Relay based communication from the ATM cells at the ATM capable
switch.
15. The method of claim 8 wherein the mapping includes: mapping the
Frame Relay based communication frames into ATM cells in accordance
with an FRF.5 standard.
16. The method of claim 8 wherein the mapping includes: mapping the
Frame Relay based communication frames into ATM cells in accordance
with an FRF.8 standard.
17. The method of claim 8 wherein the mapping includes: mapping the
Frame Relay based communication frames into ATM cells in accordance
with an FRF.8.1 standard.
18. The method of claim 8 wherein the mapping is transparent to the
DSL compatible CPE device.
Description
FIELD OF THE INVENTION
The present invention relates to a system and method for carrying
out end-to-end Frame Relay communications over an ATM based network
including a DSL link.
BACKGROUND OF THE INVENTION
It is clear that the Internet, which is the widest of all wide area
networks, is the most important development in computing and
communications in modern history. The Internet allows home and
business computers located throughout the world to communicate with
each other. Communication between these computers is possible as
the result of the connection of many large computer networks tied
together to form the Internet. Modern advancements have resulted in
the development of very high speed equipment for use in carrying
out Internet communications. The large computer networks that make
up the Internet may be connected to each other using high speed
backbone data links such as T-1, T-3, OC-1, and/or OC-3 links that
are capable of transmitting data at rates on the order of megabits
per second. It is also not uncommon for home computers to have
processing speeds on the order of a gHz, and for businesses to have
direct links to an Internet backbone.
Despite all these advances however, it has become painfully obvious
that speed of communication over the Internet will always be
limited by the speed of the slowest piece of equipment or
communication link in the chain connecting the communication end
points to the Internet backbone. Absent the special installation of
a direct high-speed data link, such as a T-1 line, an end user PC's
connection to the Internet is often initially made through the
existing telephone line infrastructure. Existing telephone links
comprise a twisted pair of copper wires running from each phone
jack in a building to a local central office. Communication from
the central offices to telephone switching centers is typically
made with a higher speed link, such as an optical fiber connection.
These higher speed links exist throughout the remainder of the
network, but do not extend past the local central offices.
Presently, the most problematic bottleneck for Internet
communication exists in the twisted copper pair link from a home or
business PC to a traditional telephone central office. Twisted
copper pairs were originally designed to carry analog
communications, i.e., voice communication. In modern times however,
communication needs have gone beyond just voice and require the
transmission of data, preferably in a digital form. The technology
to transmit digital data using an analog signal has existed for
decades in the form of modem technology. As the years have gone by,
modems have become faster and faster in an attempt to keep pace
with the increase in the speed of other network components. Modem
developers have finally reached an inherent limitation on the
amount of data that can be carried on a twisted copper pair using
an analog signal. This limitation arises from bandwidth constraints
growing out of the fact that the analog channel used for modem
communications is only 4 kHz wide. As a result, the best modems
today are able to transmit data at a rate of 56 Kilobytes per
second, provided that conditions are nearly perfect. With PC's
operating at the GHz level and digital switches and T-1 lines
operating at the MHz level, this clearly makes the modem based link
between a home or business PC and the central office the slowest
link in the Internet or other wide area network communication
scheme. Accordingly, there is a need to provide a higher rate of
communication over the existing infrastructure, namely the twisted
pair of copper wires linking most homes and businesses with local
central offices.
The desired higher rate communication over twisted copper pairs may
be provided by a relatively new technology called Digital
Subscriber Line (DSL) Technology, often referred to as xDSL where
the x signifies different variations of DSL. DSL may allow the
twisted copper pair to transmit digital information at rates
between 128 kilobytes per second to as high as several megabytes
per second. A detailed description of DSL Technology may be found
in the publication "Personal Broad Band Services: DSL and ATM" by
Jim Lane and published by Virata in 1998, which is hereby
incorporated by reference.
The concept behind DSL is as follows. Voice communications over the
twisted copper pair are carried out in a frequency range below
4,000 hertz because most human voices operate at less than 4 kHz. A
twisted copper pair, however, is capable of transmitting higher
frequency signals. The frequency range above 4 kHz, heretofore
unused, can now be used by DSL equipment to send digital signals
between homes and businesses and local central offices. What's
more, because the DSL frequencies do not overlap with the voice
frequencies, DSL communication and voice communication can occur
simultaneously over the same copper pair facility.
There is a catch to the use of DSL, however. The higher frequency
signals used to transmit DSL communications degrade as the distance
between the end phone jack and the central office increases. This
degradation is the product of both the distance and the increasing
number of "taps" on the line that occurs with increasing distance.
True highspeed DSL service (greater than 128 kbps) cannot be
carried out when the "wire distance" between the end user and the
central office is more than about three (3) miles. Luckily, central
offices have been built throughout the United States such that most
phone jacks are within a few miles "wire distance" of their
respective central office.
As noted briefly above, in recent times there have also been
important advances in the equipment (particularly in the switching
technology and regimes) that is used at the central office and at
other nodes further upstream headed towards the large Internet or
other private networking hubs. Some of the most important
advancements have involved packet type switching.
A packet is a generic term for a bundle of data that is organized
in a specific way to facilitate its transmission over a network.
Packets, also sometimes referred to as blocks, frames, or cells,
primarily comprise three types of information: the payload, the
header, and the trailer. Usually the largest part of a packet
contains the payload, i.e., the data that is to be communicated.
The header may be attached to the front of the payload. The header
includes additional digital data that tells the network where the
packet should be sent and in some instances the route that it
should take. The trailer may contain data used to detect and
correct errors in the payload that occur during transmission.
The broad category of packets may be further divided into
subcategories of variable length packets and fixed length packets.
The transmission of variable length packets is synonymous with
"frame relay" transmission. Frame relay services employ a form of
packet switching that is similar to that used for X.25 networks. In
frame relay, the packets are in the form of frames that may vary
widely in length between 0 and 4,096 octets. Because of the large
variability in the size of "frame relay" frames, they are very
suitable for the transmission of data that is not time sensitive.
For example, frame relay is not well suited for the transmission of
digital voice information because frames are designed to deliver
large chunks of digital data but at less frequent intervals.
Digital voice requires the transmission, at a regular pace, of
little pieces of data that may be used to reassemble a voice
communication after its transmission over at network. Frame relay
applications most often include private data traffic transmission
as a replacement to leased line services, such as T1.
Fixed length packets are the logical choice for digital data
transmission when variable length packets are non-optimal. The most
prevalent type of fixed length packets that are presently used are
ATM packets which have a cell length of 53 bytes, 48 of which are
for the payload. ATM is primarily used for LAN-to-LAN (Local Area
Network) applications, carrier traffic aggregation and digital
voice and video technology transmission. As a result, ATM packets
are universally useful, and ATM compatible components are commonly
used for highspeed networks, such as those that link with and
comprise the Internet.
A significant number of end user PC's are equipped to carry out
communications using Frame Relay protocol as opposed to ATM
protocol. When these PC's are connected together on a local network
with Frame Relay compatible components, they are able to easily
communicate with each using Frame Relay packets. In modern times,
however, there is an ever increasing need for end user PC's to
communicate with other end users over wide area networks, including
the Internet. Because these wide area networks are typically
equipped with ATM compatible components, such as concentrators and
switches, Frame Relay based communications could not be readily
carried out over the wide area networks. In response to this
problem, an industry group called the Frame Relay Forum (FRF)
formulated standards to govern the transmission of Frame Relay
packets over other broadband technologies, such as ATM based
networks. The inventors of the present invention are familiar with
three such standards in particular, FRF.5, FRF.8, and FRF.8.1,
which pertain to standards for the transmission of Frame Relay
packets and the interfacing of Frame Relay products with ATM based
networks. These standards are available from the Frame Relay Forum,
and are published in Frame Relay/A TM PVC Network Interworking
Implementation Agreement FRF.5, The Frame Relay Forum (Dec. 20,
1994); Frame Relay/ATM PVC Network Interworking Implementation
Agreement FRF.8, The Frame Relay Forum (Apr. 14, 1995); and Frame
Relay/ATM PVC Service Interworking Implementation Agreement
FRF.8.1, Frame Relay Forum Technical Committee (Feb. 28, 2000),
each of which is incorporated herein by reference in its
entirety.
In view of the importance of both DSL technology, and the
transmission of Frame Relay communications over ATM based networks,
for end-to-end high speed wide area and/or Internet communication,
there is a need for a system and method that integrates DSL and
Frame Relay over ATM network communications. To date, there have
been some developments in integration of DSL with Frame Relay or
ATM systems for aggregation purposes; however, there has not been a
commercially successful marriage of all three.
An example of a DSL system that is adapted to transmit data through
an ATM or a Frame Relay switch is described in U.S. Pat. No.
6,028,867 to Rawson et al. (Feb. 22, 2000), which is hereby
incorporated by reference. The Rawson patent describes a network
structure in which home PCs are connected to a Digital Subscriber
Line Access Multiplexer (DSLAM) located in a central office. The
DSLAM includes both an Asynchronous DSL (ADSL) multiplexer and an
ISDN based DSL (IDSL) multiplexer. The IDSL multiplexer provides
bandwidth of up to 128 kbps, but is not limited by the distance
between the home PC and the central office. The ADSL multiplexer
provides bandwidth of up to 6.1 Mbps in the direction from the
central office to the home PC, and up to 640 kbps in the reverse
direction so long as the local loop connecting the home PC to the
central office is less than about 14,000 feet in length. The DSLAM
is connected to a remote target (e.g. an Internet destination)
through a generic data switch. The Rawson patent does not disclose
a system or method for providing Frame Relay communication over an
ATM based network that includes a DSL link.
Another example of a DSL system that is adapted to be used with a
packet switched network is described in U.S. Pat. No. 6,081,517 to
Liu et al. (Jun. 27, 2000), which is hereby incorporated by
reference. The Liu patent discloses a broadband DSL service
provider's network. Liu describes the equipment necessary to
provide an end-user of a xDSL service with a connection at a
greater speed than traditional remote access, or Internet access
methods. The key differentiator in the Liu patent from the
above-referenced Rawson patent and the below-referenced Fosmark
patent is the description of a dynamic bandwidth allocation service
on a "call by call" basis. The Liu patent states that end-users may
dynamically request bandwidth from the network as the application
needs change, and for those allocations to be based upon efficient
network routing and cost models. Thus, from Liu it is inferred that
the customer takes an active role in determining the cost to
him/her based upon the bandwidth needed for the application being
"called" from some content located on the network. Additionally,
the Liu patent infers that the network dynamically chooses "the
PSTN 250 or WAN 260, or setting up a virtual circuit via the WAN"
based upon the needs of the end-user. While the Liu patent
discloses a typical DSL link, generally, it does not disclose a DSL
link that is capable of transmitting Frame Relay communications
over an ATM equipped network.
Still another example of a DSL system is described in U.S. Pat. No.
6,084,881 to Fosmark et al. (Jul. 4, 2000), which is hereby
incorporated by reference. The Fosmark patent discloses an endpoint
(or CPE, Customer Premises Equipment) that uses an auto-negotiation
function with the DSLAM to assign protocols associated with various
packet and cell mode transmissions. Unlike the Liu and Rawson
patents which describe an xDSL service provider's network, the
Fosmark patent describes a specific piece of equipment in an xDSL
network and is written on the behalf of an equipment
manufacturer.
Therefore, there is a need for a system and method of connecting
end users that employ Frame Relay communications to ATM host
networks in a system that includes a DSL link. In response to these
needs, the present applicants have developed a Frame Relay over
xDSL product that may be used in association with an ATM based
network.
SUMMARY OF THE INVENTION
In response to the foregoing challenges, applicants have developed
an innovative system for transmitting a Frame Relay based
communication over an ATM based network that includes a DSL link,
comprising: an end user computer; a DSL compatible Customer
Premises Equipment (CPE) device operatively connected to the end
user computer; a Digital Subscriber Line Access Multiplexer (DSLAM)
operatively connected to the CPE device; an ATM network operatively
connected to the DSLAM at a first end; and a Frame Relay capable
switch connected to the ATM network at a second end, wherein the
DSLAM is adapted to map Frame Relay based communication frames into
ATM cells for transmission over the ATM network.
Applicants have further developed an innovative method for
transmitting a Frame Relay based communication over an ATM based
network that includes a DSL link, comprising: transmitting a Frame
Relay based communication from a DSL compatible Customer Premises
Equipment (CPE) device to a Digital Subscriber Line Access
Multiplexer (DSLAM); mapping the Frame Relay based communication
into ATM cells at the DSLAM; transmitting the ATM cells across an
ATM network to a Frame Relay capable switch; and recovering the
Frame Relay based communication from the ATM cells at the Frame
Relay capable switch.
Still further, applicants have developed an innovative method for
transmitting a Frame Relay based communication over an ATM based
network that includes a DSL link, comprising: transmitting a Frame
Relay based communication from a DSL compatible Customer Premises
Equipment (CPE) device to a Digital Subscriber Line Access
Multiplexer (DSLAM); mapping the Frame Relay based communication
into ATM cells at the DSLAM; transmitting the ATM cells across an
ATM network to an ATM capable switch; and recovering the Frame
Relay based communication from the ATM cells at the ATM capable
switch.
It is to be understood that both the foregoing general description
and the following detailed description are exemplary and
explanatory only, and are not restrictive of the invention as
claimed. The accompanying drawings, which are incorporated herein
by reference and which constitute a part of this specification,
illustrate certain embodiments of the invention, and together with
the detailed description serve to explain the principles of the
present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described in conjunction with the following
drawings in which like reference numerals designate like elements
and wherein:
FIG. 1 is a schematic diagram of an embodiment of the invention
showing the interconnection of the hardware that may be used for
Frame Relay/ATM interworking to a Frame Relay termination point in
a network including a DSL link.
FIG. 2 is a schematic diagram of an alternate embodiment of the
invention showing the interconnection of the hardware that may be
used for Frame Relay/ATM service interworking to both ATM and Frame
Relay termination points in a network including a DSL link.
FIG. 3 is a schematic diagram further illustrating an embodiment of
the invention.
FIG. 4 is a schematic diagram further illustrating an embodiment of
the invention.
FIG. 5 is a schematic diagram of a DSLAM showing one configuration
that may be used in an embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
The first embodiment of the invention is described in connection
with FIG. 1, which shows a network or system 10 for carrying out
ATM/Frame Relay based data communications between computers 100 and
101 (e.g. PCs) and communication destinations such as a customer's
private Frame Relay network 400. Two alternative ways are shown in
FIG. 1 to connect the PCs 100 and 101 to the DSLAM 210 in the
Central Office 200.
The first PC 100 is connected by a 10/100 BaseT connection 110 to a
Customer Premises Equipment (CPE) device, which is an xDSL router
120. The CPE device 120 is connected to a DSLAM 210 via a twisted
pair of copper wires 160. The second PC 101 is connected to a
router 121, e.g. a V.35 compatible router, via a 10/100 BaseT
connection 111. The router 121, in turn, is connected via a
connection 130 to an xDSL compatible DSU 140. The DSU 140 is
connected to the DSLAM 210 via a twisted pair of copper wires.
There are several equipment manufacturers, such as Netopia,
Alcatel, and 3COM, that make xDSL compatible routers 120. There are
also several equipment manufacturers, such as Cisco, Alcatel, and
Lucent that make the V.35 compatible routers 121.
The DSLAM 210 is the first device encountered from the PC 100 end
of the network that is part of the xDSL service provider network
300. The function of the DSLAM 210 is to multiplex communications
received from one or more CPE devices 120 and/or 140 into a single
data stream at the Central Office 200. Providers of DSLAM equipment
include Cisco, Paradyne, Alcatel, Lucent, and Copper Mountain.
According to an embodiment of the present invention, DSLAM 210 can
be provided with Interworking Functionality that enables it to not
only multiplex DSL signals received from the CPEs 120 and 140, but
also multiplex Frame Relay based DSL signals in a manner that
allows them to be sent over an ATM based network. The Interworking
Functionality that enables Frame Relay/ATM compatibility may be
provided through implementation of FRF.5, FRF.8, or FRF.8.1
standards by the DSLAM 210. Essentially, the DSLAM 210 allows the
variable length Frame Relay frames originating with the PC 100 to
be broken down, if need be, and mapped and inserted into ATM cells
for propagation across the service provider network 300. As a
result, Frame Relay data originating from the PC 100 can be sent to
a distant Frame Relay compatible device over an ATM based network.
The DSLAM 210 is discussed in more detail below.
The xDSL circuit comprising the CPEs 120 and 140, and the DSLAM 210
may employ Layer 2 technology, where Layer 2 is the Data Link layer
in accordance with the Open Standards Interconnection model, and
wherein Layer 2 is concerned with the procedures and protocols for
operating communications lines. The Layer 2 technology employed by
the xDSL circuit may provide multiple Virtual Channels (VCs) 150
(or Permanent Virtual Connections (PVCs)), connecting the CPEs 120
and 140 with the DSLAM 210 and the aggregation and end-user
equipment connected to it.
The DSLAM 210 may be connected to an ATM concentrator 240 by a high
data-rate connection such as a DS-3 or OC-3 link 220. The ATM
concentrator 240 may be used to aggregate signals of originating
from multiple DSLAM devices. Both the DSLAM 210 and the ATM
concentrator 240 may be located in a central office 200.
Manufacturers that provide ATM concentrators include Alcatel,
Cisco, and Lucent.
In turn, the ATM concentrator 240 may be connected to an ATM switch
310 by another high-data rate connection such as a DS-3 or OC-3
link 230. Manufacturers of ATM switching equipment include Cisco,
Alcatel, and Lucent. The ATM switch 310 may be connected to a Frame
Relay capable switch 340 using ATM capable (i.e. high data-rate)
connections 320 and 330 such as DS-3 or OC-3 links.
The Frame Relay capable switch 340 at the edge of the xDSL Service
Provider's Network 300 may be connected to a Frame Relay capable
switch 410 located on the edge of the customer's network 400 to
provide connectivity to a corporate site or to the Internet
backbone 430. The connection 360 between the xDSL service provider
network 300 and the customer network 400 may be a DS-1, DS-3, or
OC-X connection. The xDSL service provider's Frame Relay capable
switch 340 may be equipped with Interworking Functionality (in
accordance with FRF.5, FRF.8, or FRF.8.1 standards) that enables it
receive the Frame Relay data that has been transmitted over the
largely ATM based network 300. Implementation of Interworking
Functionality at the Frame Relay capable switch 340 is considered
conventional, and accordingly is not explained in detail here.
The virtual channel(s) 150 established over the twisted copper pair
160 may be propagated through each link (160, 220, 230, 320, 330,
360, and 420) of the overall network 10, so that continuous
communication can occur over the network between the PCs 100 and
101 and the destination 430. Even though the data traffic to and
from the PCs 100 and 101 is carried using different protocols (e.g.
IP, ATM, and Frame Relay), there is no loss in data as a result of
the built in Frame Relay/ATM compatibility of the DSLAM 210 and the
Frame Relay capable switch 340.
With respect to the operation of the network 10 shown in FIG. 1,
the interconnection between the xDSL service provider network 300
and the customer Frame Relay network 400 takes place between two
Frame Relay capable switches, 340 and 410, respectively. The xDSL
service provider may have several switches 310 and 340 in a
Regional Metro Servicing Center (RMSC) 370 at the edge of the xDSL
service provider network 300. Frame Relay data traffic originating
on the LAN-side of the DSL CPEs 120 and 140, traverses the DSLAM
210, the ATM concentrator 240, the ATM switch 310, and the Frame
Relay capable switch 340. At the RMSC 370, the data traffic may be
aggregated over many central offices 200 into one or more data
streams over the xDSL service provider network 300 where it may
leave the network at a Frame Relay capable switch 340. After
traversing over the xDSL service provider network 300, the data
stream may enter the customer network 400 at the customer Frame
Relay network switch 410.
The mapping of Frame Relay frames to ATM cells by the xDSL service
provider enables the Frame Relay data to be carried from the
service demarc connections 110 and 111, across the xDSL service
provider network 300 to the DS-1, DS-3, or similar interconnects to
the customer network 400. This mapping occurs at the DSLAM 210. An
example of a DSLAM 210 that has been constructed and provided with
the necessary functionality to perform the mapping is shown
functionally in FIG. 5. With reference to FIG. 5, the DSLAM 210 may
include an xDSL line card 211 with an input port 212 and an output
port 213, a DSLAM backplane 214, and a DSLAM uplink card 215 with
an input from the backplane 216, a processing device for mapping
Frame Relay frames into ATM cells 217, and an output to an ATM
connection 218. The processing device 217 is programmed to map the
Frame Relay frames received from the CPE device 120 into ATM cells
for transmission on the ATM connection 220.
With renewed reference to FIG. 1, Frame Relay and/or ATM QoS
(Quality of Service) parameters are maintained by the assignment of
appropriate service parameters throughout the overall network 10
from the CPE devices 120, 121, and 140 through the ATM switches 310
and 340. End-to-end QoS in the xDSL service provider network 300
enables provisioning of specified data throughput values on a per
PVC basis in accordance with the Frame Relay and ATM service
provider's existing provisioning methodology. The DSLAM 210 may
perform LMI-to-ATM Operation, Administration, and Maintenance
(OA&M) F5 data flow conversion as needed to assure that the end
user PC 100 customer router status is propagated through the
network 10 back to the customer network 400. This may also ensure
that up/down VC status is visible from the end user router (CPE
120) and may allow end-to-end or segmented loopback functionality
and monitoring from the customer network 400.
The DSLAM 210 may be configured so that the xDSL service provider
network 300 delivers a guaranteed CIR (Committed Information Rate)
for each customer traffic-carrying PVC 150 that extends through the
xDSL service provider network.
The customer network 400 may provide any of three different xDSL
end-to-end services. The first two types of services are explained
with reference to FIG. 1. With reference to FIG. 1, the network 10
is configured such that Frame Relay communication frames may be
propagated through the service provider network 300 in a
transparent mode. Two different types of transparent mode
transmission are possible; FRF.5 over ATM AAL5 (ATM Adaptation
Layer), and FRF.8 transparent mode (collectively referred to as
"transparent mode transmission"). FRF.5 over ATM AAL5 and FRF.8
transparent mode standards may be used to provide end-to-end
networking between the Frame Relay based CPE devices 120 and 140
and the customer network Frame Relay based termination point 430.
Selection of transparent mode transmission is made by configuring
the DSLAM 210 to carry out the mapping of Frame Relay frames in
accordance with the FRF.5 over ATM AAL5 or the FRF.8 transparent
mode standards.
When transparent mode transmission is selected, the presence of the
ATM based network 300 between the CPE devices 120/140 and the Frame
Relay based customer network 400 is not "felt" by the equipment at
the customer termination point 430. In essence, the ATM based
network 300 is "transparent" to the Frame Relay equipment on the
terminal ends of the ATM network. ATM/Frame Relay interworking
functions in the xDSL service provider network at the DSLAM 210 and
the Frame Relay capable switch 340 provide the necessary functions
to transport the Frame Relay data across the ATM network without
loss of integrity and with the maintenance of PVC management
function.
The use of FRF.5 transparent mode service is desirable to Frame
Relay customers that want to keep their end users configured as
Frame Relay users. FRF.8 transparent mode service performs
similarly to FRF.5 transparent mode service, with a difference
being that the customer with FRF.8 the user at the customer network
400 does not receive additional information in the form of Backward
Explicit Congestion Notification (BECN) and Command/Response (C/R)
bits in the Frame Relay header. The BECN functionality is lost when
using FRF.8 transparent mode because FRF.8 call for the entire 2
bytes of the Frame Relay Header to be copied into the ATM cell
stream, as is required for FRF.5 transparent mode. It is expected
that FRF.8 transparent mode might be used in situations where one
of the Frame Relay devices, either the DSLAM 210 or the Frame Relay
capable switch 340 in FIG. 1 does not support FRF.5 transparent
mode, or in the event there are compatibility issues between
vendors on implementation of FRF.5. In both FRF.5 and FRF.8, all of
the terminal devices 120, 121 and 430 are Frame Relay capable
devices.
FIG. 3 illustrates a first network interworking example between
Frame Relay networks over a Broadband-integrated Services Digital
Network (B-ISDN) 30 that includes multiple ATM networks such as the
service provider network 300. The upper portion of FIG. 3 shows the
physical connection of network components, while the bottom portion
of FIG. 3 shows the corresponding communication layers involved for
each link of the network. All interworking between Frame Relay and
the B-ISDN network is done by the Interworking Functions (IWF) 212
in the DSLAMs 210 and the Frame Relay capable switch (340 in FIG.
1). The Interworking Functions of these devices may comply with
ITU-T Recommendations 1.555 and 1.365.1. The B-ISDN transport of
the Frame Relay traffic over the xDSL service provider network is
transparent to the customer. Implementation of FRF.5 transparent
mode permits the status of the CPEs 120 and 140 to be sent over the
B-ISDN network to provide the customer network (400 in FIG. 1) with
insight into such status, which is a desirable feature for some
customers.
A second embodiment of the invention is described in connection
with FIG. 2, in which like reference characters refer to like
elements, and in which the overall network 20 provides service
using a hybrid network model that may include Frame Relay and/or
ATM host-site terminations, 430 and 450, respectively. The overall
network 20 differs from the overall network 10 in FIG. 1 in that it
further includes a customer ATM switch 460, and an ATM based
customer termination point 450. The data flow and connectivity
between devices in the overall network 20 of FIG. 2 is similar to
that discussed in connection with the overall network 10 in FIG. 1.
The difference between the networks is that the customer has the
option of providing service from the Frame Relay capable CPE
devices 120 and 121 to either a Frame Relay capable termination
point 430 or to ATM capable termination points 450 in the network
20 shown in FIG. 2.
With continued reference to FIG. 2, end users whose access needs
include Frame Relay or ATM host-site access, or a hybrid mix of
Frame Relay and ATM, may implement a third type of
standard--FRF.8.1 Frame Relay/ATM Service Interworking translation
mode (referred to simply as "translation mode")--in the DSLAM 210
and the terminating Frame Relay switch 340 in the service provider
network 300. Alternatively, the translation mode functionality may
be implemented solely in the DSLAM 210 if the destination for the
traffic is solely one or more ATM based customer networks. FRF.8.1
translation mode enables both Frame Relay and ATM data
encapsulation without regard for the communication protocol used by
the underlying WAN access (i.e service provider) network 300. Using
a DSLAM with translation mode capability, the end user CPE devices
120 and 121 can send traffic to the Frame Relay terminating point
430 or the ATM terminating point 450 simultaneously over multiple
PVCs.
FIG. 4 illustrates a service interworking example between Frame
Relay networks and ATM networks. The upper portion of FIG. 4 shows
the physical connection of network components, while the bottom
portion of FIG. 4 shows the corresponding communication layers
involved for each link of the network. More specifically, FIG. 4
illustrates the service interworking between Frame Relay CPE
devices 120 and 140, the DSLAMS 210 and the ATM terminating point
450 shown in FIG. 2. The translation mode may be used when a Frame
Relay end users connected to the CPE devices 120 or 140 interact
with an ATM based terminating point 450 and the ATM terminating
point performs no Frame Relay specific functions, and the Frame
Relay CPE devices perform no ATM service specific functions. All
interworking is performed by the Interworking Function 212
implemented in the DSLAMs 210. The Interworking Function converts
the Q.922 Frame Relay frames to and from the ATM AAL5 PDUs.
Another scenario where translation mode may be used is in the
interworking between the CPE devices 120 or 140 and the Frame Relay
based terminating point 440. In this scenario the Interworking
Function is carried out between the DSLAM 210 and the Frame Relay
capable switch 340 (shown in FIG. 2). With reference to FIG. 2, the
Frame Relay capable switch 340 re-encapsulates the data back to
Frame Relay frames and sends the traffic to the customer Frame
Relay capable switch 410 and then to the customer Frame Relay
terminating point 440. This scenario might be used if the service
provider wants to use the same type of configuration for all of the
end users of the customer in the service provider network 300.
It will be apparent to those skilled in the art that various
modifications and variations may be made in the preparation and
configuration of the present invention without departing from the
scope and spirit of the present invention. Thus, it is intended
that the present invention cover all of the modifications and
variations of the invention so long as they come within the scope
of the following claims.
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